xfs_io: only print the header once when dumping fsmap in csv format

Only print the column names once when we're dumping fsmap information in
csv format.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/io/fsmap.c b/io/fsmap.c
index 4b21759..9f179fa 100644
--- a/io/fsmap.c
+++ b/io/fsmap.c
@@ -116,7 +116,8 @@
 	struct fsmap		*p;
 	char			*fork;
 
-	printf(_("EXT,MAJOR,MINOR,PSTART,PEND,OWNER,OSTART,OEND,LENGTH\n"));
+	if (*nr == 0)
+		printf(_("EXT,MAJOR,MINOR,PSTART,PEND,OWNER,OSTART,OEND,LENGTH\n"));
 	for (i = 0, p = head->fmh_recs; i < head->fmh_entries; i++, p++) {
 		printf("%llu,%u,%u,%lld,%lld,", i + (*nr),
 			major(p->fmr_device), minor(p->fmr_device),